#include "base64.h"

#include <contrib/libs/base64/avx2/libbase64.h>
#include <contrib/libs/base64/ssse3/libbase64.h>
#include <contrib/libs/base64/neon32/libbase64.h>
#include <contrib/libs/base64/neon64/libbase64.h>
#include <contrib/libs/base64/plain32/libbase64.h>
#include <contrib/libs/base64/plain64/libbase64.h>

#include <util/generic/yexception.h>
#include <util/system/cpu_id.h>
#include <util/system/platform.h>

#include <cstdlib>

namespace {
    struct TImpl {
        void (*Encode)(const char* src, size_t srclen, char* out, size_t* outlen);
        int (*Decode)(const char* src, size_t srclen, char* out, size_t* outlen);

        TImpl() {
#if defined(_arm32_)
            const bool haveNEON32 = true;
#else
            const bool haveNEON32 = false;
#endif

#if defined(_arm64_)
            const bool haveNEON64 = true;
#else
            const bool haveNEON64 = false;
#endif

            if (NX86::HaveAVX() && NX86::HaveAVX2()) {
                Encode = avx2_base64_encode;
                Decode = avx2_base64_decode;
            } else if (NX86::HaveSSSE3()) {
                Encode = ssse3_base64_encode;
                Decode = ssse3_base64_decode;
            } else if (haveNEON64) {
                Encode = neon64_base64_encode;
                Decode = neon64_base64_decode;
            } else if (haveNEON32) {
                Encode = neon32_base64_encode;
                Decode = neon32_base64_decode;
            } else if (sizeof(void*) == 8) {
                // running on a 64 bit platform
                Encode = plain64_base64_encode;
                Decode = plain64_base64_decode;
            } else if (sizeof(void*) == 4) {
                // running on a 32 bit platform (actually impossible in Arcadia)
                Encode = plain32_base64_encode;
                Decode = plain32_base64_decode;
            } else {
                // failed to find appropriate implementation
                std::abort();
            }
        }
    };

    static const TImpl GetImpl() {
        static const TImpl IMPL;
        return IMPL;
    }
}

static const char base64_etab_std[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char base64_bkw[] = {
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',                // 0..15
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',                // 16..31
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\76', '\0', '\76', '\0', '\77',             // 32.47
    '\64', '\65', '\66', '\67', '\70', '\71', '\72', '\73', '\74', '\75', '\0', '\0', '\0', '\0', '\0', '\0',      // 48..63
    '\0', '\0', '\1', '\2', '\3', '\4', '\5', '\6', '\7', '\10', '\11', '\12', '\13', '\14', '\15', '\16',         // 64..79
    '\17', '\20', '\21', '\22', '\23', '\24', '\25', '\26', '\27', '\30', '\31', '\0', '\0', '\0', '\0', '\77',    // 80..95
    '\0', '\32', '\33', '\34', '\35', '\36', '\37', '\40', '\41', '\42', '\43', '\44', '\45', '\46', '\47', '\50', // 96..111
    '\51', '\52', '\53', '\54', '\55', '\56', '\57', '\60', '\61', '\62', '\63', '\0', '\0', '\0', '\0', '\0',     // 112..127
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',                // 128..143
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0',
    '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0'};

static_assert(Y_ARRAY_SIZE(base64_bkw) == 256, "wrong size");

// Base64 for url encoding, RFC3548
static const char base64_etab_url[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

template <bool urlVersion>
static inline char* Base64EncodeImpl(char* outstr, const unsigned char* instr, size_t len) {
    const char* base64_etab = (urlVersion ? base64_etab_url : base64_etab_std);
    const char last = (urlVersion ? ',' : '=');

    size_t idx = 0;

    while (idx < len) {
        if (idx % 3 == 0) {
            *outstr++ = base64_etab[(int)(instr[idx] >> 2)];
        } else if (idx % 3 == 1) {
            *outstr++ = base64_etab[(int)(((instr[idx - 1] << 4) & 0x30) | ((instr[idx] >> 4) & 0x0f))];
            char c3 = idx + 1 < len ? instr[idx + 1] : '\0';
            *outstr++ = base64_etab[(int)(((instr[idx] << 2) & 0x3c) | ((c3 >> 6) & 0x03))];
        } else {
            *outstr++ = base64_etab[(int)(instr[idx] & 0x3f)];
        }

        idx++;
    }

    if (idx % 3 == 1) {
        *outstr++ = base64_etab[(int)((instr[idx - 1] << 4) & 0x30)];
        *outstr++ = last;
        *outstr++ = last;
    } else if (idx % 3 == 2) {
        *outstr++ = last;
    }

    *outstr = 0;

    return outstr;
}

static char* Base64EncodePlain(char* outstr, const unsigned char* instr, size_t len) {
    return Base64EncodeImpl<false>(outstr, instr, len);
}

char* Base64EncodeUrl(char* outstr, const unsigned char* instr, size_t len) {
    return Base64EncodeImpl<true>(outstr, instr, len);
}

inline void uudecode_1(char* dst, unsigned char* src) {
    dst[0] = char((base64_bkw[src[0]] << 2) | (base64_bkw[src[1]] >> 4));
    dst[1] = char((base64_bkw[src[1]] << 4) | (base64_bkw[src[2]] >> 2));
    dst[2] = char((base64_bkw[src[2]] << 6) | base64_bkw[src[3]]);
}

static size_t Base64DecodePlain(void* dst, const char* b, const char* e) {
    size_t n = 0;
    while (b < e) {
        uudecode_1((char*)dst + n, (unsigned char*)b);

        b += 4;
        n += 3;
    }

    if (n > 0) {
        if (b[-1] == ',' || b[-1] == '=') {
            n--;

            if (b[-2] == ',' || b[-2] == '=') {
                n--;
            }
        }
    }

    return n;
}

// Table for Base64StrictDecode
static const char base64_bkw_strict[] =
    "\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100"
    "\100\100\100\100\100\100\100\100\100\100\100\76\101\76\100\77\64\65\66\67\70\71\72\73\74\75\100\100\100\101\100\100"
    "\100\0\1\2\3\4\5\6\7\10\11\12\13\14\15\16\17\20\21\22\23\24\25\26\27\30\31\100\100\100\100\77"
    "\100\32\33\34\35\36\37\40\41\42\43\44\45\46\47\50\51\52\53\54\55\56\57\60\61\62\63\100\100\100\100\100"
    "\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100"
    "\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100"
    "\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100"
    "\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100\100";

size_t Base64StrictDecode(void* out, const char* b, const char* e) {
    char* dst = (char*)out;
    const unsigned char* src = (unsigned char*)b;
    const unsigned char* const end = (unsigned char*)e;

    Y_ENSURE(!((e - b) % 4), "incorrect input length for base64 decode");

    while (src < end) {
        const char zeroth = base64_bkw_strict[src[0]];
        const char first = base64_bkw_strict[src[1]];
        const char second = base64_bkw_strict[src[2]];
        const char third = base64_bkw_strict[src[3]];

        constexpr char invalid = 64;
        constexpr char padding = 65;
        if (Y_UNLIKELY(zeroth == invalid || first == invalid ||
                       second == invalid || third == invalid ||
                       zeroth == padding || first == padding)) {
            ythrow yexception() << "invalid character in input";
        }

        dst[0] = char((zeroth << 2) | (first >> 4));
        dst[1] = char((first << 4) | (second >> 2));
        dst[2] = char((second << 6) | third);

        src += 4;
        dst += 3;

        if (src[-1] == ',' || src[-1] == '=') {
            --dst;

            if (src[-2] == ',' || src[-2] == '=') {
                --dst;
            }
        } else if (Y_UNLIKELY(src[-2] == ',' || src[-2] == '=')) {
            ythrow yexception() << "incorrect padding";
        }
    }

    return dst - (char*)out;
}

size_t Base64Decode(void* dst, const char* b, const char* e) {
    static const TImpl IMPL = GetImpl();
    const auto size = e - b;
    Y_ENSURE(!(size % 4), "incorrect input length for base64 decode");
    if (Y_LIKELY(size < 8)) {
        return Base64DecodePlain(dst, b, e);
    }

    size_t outLen;
    IMPL.Decode(b, size, (char*)dst, &outLen);

    return outLen;
}

TString Base64DecodeUneven(const TStringBuf s) {
    if (s.length() % 4 == 0) {
        return Base64Decode(s);
    }

    // padding to 4
    return Base64Decode(TString(s) + TString(4 - (s.length() % 4), '='));
}

char* Base64Encode(char* outstr, const unsigned char* instr, size_t len) {
    static const TImpl IMPL = GetImpl();
    if (Y_LIKELY(len < 8)) {
        return Base64EncodePlain(outstr, instr, len);
    }

    size_t outLen;
    IMPL.Encode((char*)instr, len, outstr, &outLen);

    *(outstr + outLen) = '\0';
    return outstr + outLen;
}
